Arrangement for applying fuel injection corrections as a function of speed, in internal combustion engines

ABSTRACT

An arrangement by which corrections are applied to the pulses which open electromagnetically controlled valves for fuel injection in internal combustion engines. The opening pulses for the valves are generated by a monostable multivibrator to which a control voltage is applied. The multivibrator emits substantially rectangular-shaped pulses, the durations of which are controlled as a function of speed of the engine, through the control voltage. The control voltage has characteristics variable periodically in synchronism with the pulses provided by the monostable multivibrator. A storage capacitor integrates the control voltage, and charging sources connected to the capacitor have different internal resistances. The charging sources are switched and connected to the capacitor in predetermined sequence.

United States Patent [72] Inventor Wolf Wessel Stuttgart, Germany [2]]Appl. No. 67,851 [22] Filed Aug. 28, I970 [45] Patented Nov. 16, 1971Primary Examiner Laurence M. Goodridge Ass/slant Examiner-Ronald 8. CoxAllornev- Michael S. Striker ABSTRACT:

[73] Assignee Robert Bosch GmbII Stuttgart, Germany [32] Priority Sept.4, 1969 [33] Germany An arrangement by which corrections are apulseswhich open electroma plied to the p gnetically controlled injection ininternal combustion en valves for fuel gines. The generated by amonostable [54] ARRANGEMENT FOR APPLYING FUEL opening pulses for thevalves are INJECTION CORRECTIONS AS A FUNCTION OF SPEED IN INTERNALCOMBUSTION ENGINES multivibrator to which a control voltage is applled.The mul- 20 chilns6mlwing Figs tivibrator emits substantiallyrectangular-shaped pulses. the

durations of which are controlled as a function of 5 engine. through thecontrol volta characteristics variable periodic ulses provided by themonost emee mhmm .I nsmm da 60 A p m. .B I. O mm r. m O .I m w e h h .mmC V.C sum 3 [52] US. [51] Int. [50] FIeldoISearch..

capacitor integrates the control voltage, and charging sources connectedto the capacitor have different internal resist The c [56] ReferencesCited UNITED STATES PATENTS 2,883,976 4/l959 Woodward.

ances. arging sources are switched and connected to the capacitor inpredetermined sequence.

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his ATTORNEY BACKGROUND OF THE INVENTION In. fuel injection arrangementsof this species, the quantity of fuel injected after each operatingcycle of an internal combustion engine is determined by the openingduration of the associated fuel injection valve. This valve admits thefuel under substantially constant pressure. To vary the duration of thepulse applied to the valve, the feedback circuit of the monostablemultivibrator includes an electrical energy storage element, whichconsists of an inductor or choke. The magnitude of the inductor or chokeis adjusted or varied in accordance with the pressure prevailing behindthe throttle flap within the intake manifold. In order to achieve theapplication of correction to the pulse duration, which are dependentupon the rotational speed, it is possible to provide for the shorteningor extension of the unstable state of the multivibrator through atime-dependent variable control voltage. The feedback provisions of sucha multivibrator are otherwise nonvariant. Thus, the duration of theunstable state of the multivibrator may be varied through a controlvoltage which varies as a function of time. The control voltage isgenerated at the end of a pulse and is producedthrough a control circuitwhich has two or more switching transistors.

In one control arrangement of the preceding species known in the art,two storage capacitors are provided in one interconnected chain throughresistors. The voltage at the end of the chain is coupled to theemitter-base circuit of the input transistor of the monostablemultivibrator. Such coupling is achieved through a resistor. In view ofsuch coupling, it is essential to use relatively large storagecapacitors, since the resistors which function in conjunction with thecapacitors, can only have substantially small magnitudes. In addition,difficulty is incurred in matching such known control circuit to thespeed characteristics of a particular internal combustion engine. Thus,when varying individual resistance values, considerably complex andincomprehensible effects take place upon the characteristics of thecontrol voltage and the duration of the opening pulses for the valves.

In order to avoid the difficulties, the control voltage, in accordancewith the present invention, is produced from a circuit which appliesself-corrections to the opening pulses as a function of engine speed. Atleast two charging sources of different internal resistance areprovided, in accordance with the present invention, for the storagecapacitor. These charging sources are connected to the storage capacitorone after another, so that the previously effective charging sourcebecomes disconnected when the next charging source takes effect.

SUMMARY OF THE INVENTION A control arrangement for the injection of fuelin internal combustion engines. The fuel is injected through anelectromagnetically controlled valve which is opened through theapplication of a pulse. The opening pulses for the valves are generatedby a monostable multivibrator which provides substantiallyrectangular-shaped pulses with durations equal to the opening intervalof the fuel injection valves. A control voltage is generated and appliedto the multivibrator at a circuit point where the potential influencesthe ends of the pulses, and thereby the ends of the unstable state ofthe multivibrator. The control voltage varies the duration of the pulsesignals as a function of the speed of the engine. The control voltage,furthermore, has characteristics which vary periodically in synchronismwith the pulse signals. A storage capacitor is used for integrating thecontrol voltage, and the capacitor becomes charged through at least twocharging sources connected thereto, and having different internalresistances. A switching circuit connected to the charging sourcesconnects one or the other sources to the capacitor. Two capacitors maybe used in which case the coupling diodes prevail between them. Whensuch two capacitors are used, that capacitor is operative which has themore positive voltage across it.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is an electrical circuit diagramand shows the components and their interconnections of the controldevice for internal combustion engines, in accordance with the presentinvention;

FIG. 2 is a graphical representation as a function of time, of thecorrection applied to the opening duration for the fuel injectionvalves, as produced by the circuit diagram of FIG. 1;

FIG. 3 is an electrical circuit diagram of another embodiment of thearrangement of FIG. I;

FIG. 4 is a graphical representation as a function of time of thecontrol voltage generated by the circuit diagram of FIG. 3;

FIG. 5 is still another embodiment of the control arrangement of FIG. 1;and

FIG. 6 is a graphical representation as a function of time of thecontrol voltage generated through the circuit arrangement of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, andin particular to FIG. I, the fuel injection arrangement is adapted todrive a four-cylinder internal combustion engine 1. The spark plugs 2 ofthis engine are connected to a high-voltage ignition arrangement, notshown. In direct proximity of the inlet valves, not shown, for theengine, are electromagnetically actuated injection valves 4. Thesevalves are arranged so that one valve is providedfor each branch leadingfrom the intake manifold 3. Fuel from a fuel distributor 6, istransmitted to each electromagnetically actuated injection valve 4,through fuel lines 5. A pump 7 driven by an electric motor maintains thepressure of the fuel within the distributor 6 and fuel lines 5 at apressure of substantially 2 atmospheres.

Each fuel injection valve 4 possesses a magnetizing coil, not shownhaving one tenninal connected to ground potential. The other terminal ofthe coil are connected through the circuit lines 8 to resistors 9. Thus,each one of the magnetizing coils of a valve is connected through oneline 8 to one resistor 9. The resistors 9 are paired, and each of twopairs of resistors 9 are connected together, at one terminal, and to thecollector of one of two transistors 10 and 11.

These transistors are power transistors which belong to an electronicregulating and control circuit described in greater detail in whatfollows:

The regulating and control circuit includes, in addition to the powertransistors 10 and 11, a monostable multivibrator 12 for generatingelectrical pulse signals. This monostable multivibrator intransistorized form, is outlined through a border designated by brokenlines. The monostable multivibrator has an input transistor 13 and anoutput transistor 14, as well as an inductor or ferromagnetic choke 15for the purpose of serving as a timing element.

The choke or inductor 15 is constructed in the form of a transformer,and has a displaceable armature 16. The armature is, in turn, secured toa displacement rod 17 which is connected to the membrane, not shown, ofa pressure sensor 18. The pressure-sensing device 18 is connected withits suction side, to the intake manifold 3 of the internal combustionengine. The pressure sensor l8, furthermore, is located directly behindan adjustable throttle flap I0 which may be adjusted or displaced to afoot lever or pedal 19. When the pressure drops within the intakemanifold, the armature I6 is moved in the direction of the arrow shownin the drawing. in this manner, the airgap of the transformer isincreased and the inductance of the primary winding 21 of thetransformer is decreased when the pressure within the intake manifold 3drops or is decreased and the armature 16 moves in the direction of thearrow shown.

The secondary winding 22 of the transformer has one tenninal connectedto the base of the input transistor 13 and to a resistor 24. The othertenninal of the winding 22 is connected to the circuit junction H. Aresistor 25 is connected between this circuit junction H and thepositive voltage supply line 23. A resistor 26, furthermore, isconnected between the negative voltage supply line and the circuitjunction H. The negative voltage supply line 30 is also connected toground potential. The positive and negative voltage supply lines 23 and30 are connected to a l2-volt battery, not shown, which supply theelectrical energy to the respective terminals.

The transistors 13 and 14 are both of the NPN-type, and both have theiremitters connected to the negative voltage supply line 30. The collectorof the input transistor 13 is connected through a resistor 27, to thepositive voltage supply line 23. The collector of the transistor 14, onthe other hand, leads to the positive supply line 23, through a seriescircuit consisting of the primary winding 21 of the transformer 15 and aresistor 28 connected in series therewith. The base of the transistor 14is connected, through a resistor 29, with the collector of thetransistor 13. A capacitor 31 used for differentiating purposes isconnected between the base of the transistor 13 and the fixed contact 32of the switch having a movable contact 33 connected to the negativesupply line 30. The movable arm of this switch is actuated or operatedthrough a two-lobed cam which is mechanically coupled to the crank shaft34 of the engine. For each rotation of the crank shaft of the engine,the two-lobed cam 35 becomes closed once and thereby causes thetransistor 13 to become nonconducting.

For purposes of charging and discharging the capacitor 31, the switchingcontact 32 leads to the positive voltage supply line 23, through aresistor 36. Another resistor 24 is connected between the voltage supplyline 23 and the other electrode of the capacitor 31. The junction of thecapacitor 31 and the resistor 24, is also connected to one terminal ofthe secondary winding 22.

Before describing further the details of these circuit components of thecontrol arrangement, a description is provided on how the openingduration of the fuel injection valves 4 is determined by the pulsecurrents J, for each closure of the switching contacts 32,33. The pulsecurrents .l vary with variations in pressure within the intake manifold3 and, thereby, the inductance of the primary winding 21.

Directly before the switching arm 33 is actuated to a circuit closureposition, the input transistor 13 is in the conducting state, andthereby maintains the output transistor 14 cut off. As soon as theswitching arm 33 becomes pressed, however, against the switching contact32, through the action of the cam 35, the stored charge across thecapacitor 31 causes a drop in the base potential of the input transistor13. The arrangement is such that the base potential of the inputtransistor 13 becomes thereby dropped below the potential of thenegative voltage supply line 30. As a result, the transistor 13 becomescut off and the multivibrator l2 switches to its unstable operatingstate. In this unstable state, the transistor 14 conducts. Thetransistor 14 has then applied to its collector, a current which risesexponentially, This exponentially rising current flows through theprimary winding 21 and gives rise to an increasing magnetic field in thecore and armature 16 of the transformer. The increase in current occursmore rapidly, the larger the airgap and the smaller the inductance oftheprimary winding 21 resulting from the increase in the airgap.

With such increase or rise in current, a voltage is induced within thesecondary winding 22. From the instant that the switching contacts 32and 33 are closed, this induced voltage becomes reduced exponentiallyfrom a maximum value, at a reducing rate determined by the magnitude ofthe inductance. The induced voltage is of the polarity so that it tendsto maintain the input transistor 13 cut off, whereby the positive basepotential determined by the resistors 24,25 and 26 is opposed. Thus,such base potential tends to return the input transistor 13 to itsstable state in which it is in the conducting operative state. Thissituation occurs when the induced voltage in the secondary winding 22has a magnitude which is smaller than the base potential.

As long as transistor 13 is cut off or is in the nonconducting state,the conducting transistor 14 maintains the power transistors 10 or 11also in the conducting state, through an amplifier 38. However, as soonas transistor 13 returns to its stable conducting state, the transistor14, 10 and 1! become again cut off. The duration of the pulses .l whichswitch the valve 4 to their opening position, extends thereby from theinstant or closure of the switch 33 to the instant of time at which theoutput transistor 14 becomes cut off and the input transistor 13 becomesagain conducting. When the inductance of the primary winding 21decreases with drop in pressure within the intake manifold 3, and thecollector current of the transistor 14 rises more rapidly as a result,the induced voltage within the secondary winding 22 also decreases morerapidly. The input transistor 13, at the same time, returns to itsconducting state at an earlier instant of time. The valves 4 becomethereby closed at an earlier instant of time in this case, than in thepreceding case in which a higher inductance and higher pressureprevails.

Through the variation in the inductance of the primary winding 21, asdescribed above, the duration of the opening pulse J for the injectionvalves becomes matched to the pressure of the internal combustionengine. Experiments during running conditions have shown that the fuelquantity to be injected must be varied as a function of rotationalspeed, in addition to the magnitude of vacuum pressure. Since the pulsedurations which are set as a function of the prevailing pressure, andsince these pulse durations are independent of the rotational speed ofthe engine for any value of the pressure, the regulating and controlcircuit of FIG. 1 has an additional control circuit A, through which thevoltage prevailing between the circuit junction H and the negativevoltage supply line 30 become periodically varied in rhythm to theinjection processes. A control voltage U,, shown in H6. 2, has afunction of time, is produced by the control circuit. This controlcircuit U, is composed exclusively of exponential parts and sections ofconstant instantaneous values.

The control circuit A includes a first transistor T with base connectedto the positive voltage supply line 23, through a resistor R The seriescircuit ofa capacitor C and resistor 39, is connected between thecircuit junction G and the base of the transistor T,. A resistor 27 isconnected between the same circuit junction G and the positive voltagesupply line 23. The circuit junction G corresponds to the collector ofthe transistor 13. Similar to the first switching transistor T,, asecond transistor T has its emitter connected to the negative voltagesupply line 30, and its base connected to the collector of thetransistor T through a coupling resistor 40.

Two resistors R and R are connected in series and between the collectorof transistor T and the positive voltage supply line 23. The junctionbetween these two resistors R and R, is connected to the cathode of adiode D The collector of the transistor T furthermore, is connected to aresistor 41 which, in turn, is connected in series with a capacitor C,One electrode of this capacitor C is connected to the base of a thirdtransistor T This transistor T as well as a fourth transistor T, are ofthe PNP-type. The emitters of both of these transistors T and T areconnected to the positive voltage supply line 23. The base of thetransistor T is connected, through a resistor, R to the negative voltagesupply line 30. The transistor T; has, thereby, the tendency to beconducting in the quiescent state of the control circuit, as does thetransistor T,. This transistor also has its base connected to thenegative voltage supply line 30, through a resistor R Both of thesetransistors form source of charge through their different internalresistances, and they feed a common storage capacitor C,. The controlvoltage U,, shown in FIG. 2, appears across this storage capacitor CThis control voltages is applied to the circuit junction H of thesecondary winding 22, through a transistor T which operates as anemitter follower.

Two resistors R,, and R,, are arranged between the collector of thetransistor T, and the negative voltage supply line 30. One terminal of aresistor R,,, is connected to the junction of the two resistors R,, andR,,, whereas the other terminal of the resistor R,,, is connected to theanodes of two diodes D, and D The cathode of the diode D, is connectedto one electrode of the capacitor C,, and also to the anode of the diodeD,. The cathode of the diode D,, on the other hand, is connected to thejunction of two resistors R,, and R,,, which form a voltage divider. Theanode of a diode D is connected directly to the collector of atransistor T while the cathode of this diode D leads to the negativevoltage supply line through a resistor -R,,,. The cathode of the diode Dis also connected to the base of the transistor T,, through a capacitorC Analogous to the transistor T,,, a series circuit of two resistorsR,,, and R,, is connected between the collector of the transistor T, andthe negative voltage supply line 30. A resistor R,,, is connected, withone terminal, to the junction of resistors R,, and R,,. The otherterminal of the resistor R,,, is connected to the anodes of two diodesD, and D,,. The cathode of the diode D is connected to the cathode ofthe diode D,, as well as to the base of the transistor T and oneelectrode of the storage capacitor C,. The cathode of the diode D,,, onthe other hand, is connected directly to the collector of the transistorT,,.

The control circuit A, moreover, includes two further voltage dividersof which one divider consists of resistors R,, and R The junction ofthese two resistors R,, and R is connected to a further resistor R,,,which leads to the anodes of two diodes D, and D The other voltagedivider consists of resistors R,, and R,,, with the junction betweenthese two resistors is connected to the cathode of a diode D The cathodeof the diode D is connected to the capacitor C,.

in the operation of the control circuit A, assume that a negative stepvoltage is applied to the base of transistor T,, through the couplingcapacitor C,, at the instant t=0 denoting the end of an injection pulse,in FIG. 2, from the control multivibrator 12. As a result, thetransistor T, remains nonconducting or cut off for as long as couplingcapacitor C, remains to be charged through the resistor R, to the extentthat base current is made available for the transistor T,. During thenonconducting period of the transistor T, next to the instant of timet=0, the transistor T conducts and discharges the storage capacitor C,through the diode D,, until a residual voltage U remains. This residualvoltage is determined through the magnitudes of the resistors R, and R,,which constitute a voltage di vider. When the transistor T, becomesagain conducting at the instant of time T, after the capacitor C, hasagain been charged, the transistor T becomes cut off. The diode D, isalso then nonconducting, and the discharge of the storage capacitor C,is terminated. When the transistor T returns to its cutoff ornonconducting state, a positive step voltage appears at the collector ofthis transistor. This stop voltage is, in turn, transmitted to the baseof the transistor T,,, through the coupling capacitor C The transistor Tremains thereby nonconducting until the capacitor C, has become charged,through the resistor R to the extent that base current again prevails atthe transistor T,. This occurs at the instant of time t,. Until thisinstant of time is attained, the nonconducting transistor T, has anegative potential applied to its collector through the resistors R,,and R,,. As a result, the diode D, is nonconducting. At the same time,the potential of the circuit junction P between the resistor R,,, andthe diode D is maintained at negative potential, through the diode D,,.The diode D is thereby also nonconducting. The charging of the storagecapacitor C, result thereafter from the instant of time t,, only throughthe resistor R,, and the diode D The voltage U,, across the storagecapacitor C, then tends toward a voltage limit U,, with a time constantT, This time constant is the product of the capacitance of the storagecapacitor C, and the magnitude of the resistor R,,. The voltage limit U,is determined by the voltage divider with the resistors R,, and R Whenthe voltage U, has attained the value U,,, through the voltage-dividingresistors R and R,,, at the instant of time t, then the diode D becomesconducting. In that state of the diode D the diode prevents furthercurrent flow to the capacitor C,, through the diode D The controlvoltage U,, across the storage capacitor C, remains, thereby, at thevalue U,,, until the instant of time t,, at which the transistor T, isagain conducting.

When the transistor T becomes again conducting at the instant of timet,, a positive step voltage appears at its collector. This step voltageis transmitted to the base of the transistor T,, through the couplingcapacitor C The transistor T, is, thereby, turned off until the instantof time t,. During that interval, the capacitor C becomes chargedthrough the resistor R to the extent that base current at the transistorT, again prevails. in the tumed-off state of the transistor T,, negativepotential is applied to the collector of the transistor through theresistors R,,, and R,,, so that the diode D is also nonconducting.

From the instant of time t,, charging current for the storage capacitorC, can flow only through the resistor R,, and the diode D,, as well asthe resistor R,, and the transistor T under the preceding conditions. Asa result, the voltage U, across the storage capacitor C, tends towards alimit U,, with a time constant T This time constant is approximately theproduct of the capacitance of the capacitance of the capacitor C, andthe magnitude of resistor R,,. The voltage limit U is determined by thevoltage divider consisting of resistors R,, and R,, in the collectorcircuit of the transistor T When the voltage U, attains the value Uthrough further increase at the instant of time t the diode D, becomesconducting. The voltage U,,, is determined through the relativemagnitudes of the resistors R,, and R,, which constitute a voltagedivider. With the diode D made conducting, charging current is preventedto the capacitor C,, through the diode D,. From the instant of time t tothe instant of time t at which point the transistor T is againconducting, because the coupling capacitor C, has then becomesufficiently charged, the voltage U, across the capacitor C, remains atthe constant value U,,

From the instant of time T charging current can flow to the capacitor C,through the then conducting transistor T,, through the collectorresistor R,,, through the resistor R,,, and through the diode D,. Withsuch charging of the storage capacitor C,, the voltage U, across thecapacitor also increases exponentially. The rate at which the voltage U,rises, is determined by the time constant T which corresponds to theproduct of the capacitance of the capacitor C, and the magnitude of theresistor R,,. Similarly to the two preceding exponential sections thatwere described, the voltage U,, tends to a limit value which is notdescribed in FIG. 2, but which is determined by the relative magnitudesof the resistors R,,, and R,, constituting a voltage divider in thecollector circuit of the transistor T,.

When the internal combustion engine operates very slowly, the durationbetween the ends of one opening pulse and the end of a subsequentopening pulse is larger than the interval between time F0 to t shown inFIG. 2. The end of the next opening pulse, therefore, becomes determinedthrough the control voltage U,, beginning with the portion T, at theinstant t,. For this case a very low rotational speed of the engine, theend of the subsequent opening pulse is represented through the timeinstant t,. A new period begins at that instant of time, in which thecontrol voltage runs in the same manner as between the time instant t tothe instant t,. This situation applies for as long as the low rotationalspeed is maintained. The higher the rotational speed, however, thecloser the time instant t, moves to the instant t,. The spacing of thetime instant t, from the instant t#), at which point the period begins.is chosen to be so small that it is smaller than the shortest period ofinjection which prevails at maximum rotational speed.

The curve shown in FIG. 2 as a function of time and representing thecontrol voltage U,, has exclusively the increasing tendency and tothereby deliver longer injection pulses with rise in engine speed, whenall other parameters and conditions remain the same. For this reason, amodified control arrangement is shown in FIG. 3, which can be used inplace of the control circuit A in FIG. 1. This arrangement of FIG. 3 canthen provide a control voltage which has an increasing function as wellas decreasing characteristics. The control voltage curve of thearrangement of FIG. 3 is shown in FIG. 4 as a function of time.Components in the control arrangement of FIG. 3 which are the same asthose in the control circuit A in FIG. 1, are denoted by the samereference numeral. In addition to the circuit configuration of FIG. I, asecond storage capacitor C is used for the arrangement of FIG. 3. Thiscapacitor C produces the decreasing charac teristics at the beginning ofthe control voltage curve shown in FIG. 4.

This second storage capacitor C, is connected, through a diode D,, tothe base ofa transistor T operating in the form of an emitter follower.The capacitor C thereby, functions as a parallel component to thecapacitor C which is connected to the base of this transistor T throughan additional diode D,;,. In addition to both of the voltages which aredependent on charging state of the capacitors C, and C,,, a thirdvoltage may be applied to the transistor T to the diode D This thirdvoltage is taken or tapped from the junction of two resistors R and Rforming a voltage divider. Through the decoupling function of diodes D,,and D and D that one of the three voltages is used to control thetransistor T,,, which has the most positive potential.

In operation of the circuitry, the diode D,, which is connected to thecollector of transistor T,, becomes nonconducting as soon as thetransistor T, becomes nonconducting as soon as the transistor T, becomesnonconducting at the instant of time t=0, at the end of an openingpulse, through the capacitor C,. The capacitor C,, can then chargeexponentially, through the diode D,,,, in accordance with FIG. 4. Thecapacitor can then become charged to a maximum value of U, which isdetermined through the relative magnitudes of the two resistors R and Rwhich form a voltage divider. By choosing sufficiently small resistancesfor the voltage-dividing resistors R,, and R it is possible to achievethat during the charging process of the capacitor C,, very rapid voltagechanges take place which are already larger than the rapidly droppingresidual voltage across the discharging capacitor C from the instant oftime t=0. This time instant is shown in FIG. 4 by t From this instant oftime, the control voltage U, is determined by the electrode of thesecond storage capacitor C,, with the larger positive potential.

The turned-off state of the transistor T, is maintained until the timeinstant t,, as described in the preceding embodiment. At this timeinstant t,, the capacitor C, has discharged to the extent thatsufficient current can flow through the emitterbase path of thetransistor T, so as to make this transistor again conducting. Theconducting transistor T, then short circuits the voltage-dividingresistor R through the diode D which also conducts. In this manner, thediode D is nonconductlng and the second storage capacitor can discharge,from the time instant t,, through the parallel resistor R This dischargeprocess takes place with a time constant T,., which depends upon thecapacitance value of the capacitor C,, and the magnitude of the resistorR From the instant of time t, the voltage across the capacitor C, dropsbelow the value U which is determined by the voltage-dividing resistorsR and R As a result, the control voltage maintains this voltage valuefrom the time instant t,

In accordance with the description of the first embodiment, the storagecapacitor C becomes charged, through the resistor R, and the diode Dfrom the instant of time t,. The voltage across the storage capacitorthen attains the set value U., which is established by the resistors Rand R forming a voltage divider. This voltage value across the storagecapacitor is attained at the instant of time t,,,.

From that same instant of time, the voltage across the capacitor C.remains positive in comparison with the voltage across the capacitorC,,. In this manner, the control voltage U, at the transistor T isfunctionally determined through the diode D,,, which is now conducting.

With the embodiment of the control arrangement of FIG. 5, it is shownhow the control voltage characteristic U,, shown in FIG. 6, is obtainedwith a single storage capacitor C,,. This functional curve of U, in FIG.6, has increasing as well as decreasing sections.

The circuit arrangement shown in FIG. 5 is used for generating thecharacteristic of the control voltage U,, shown in FIG. 6. This circuitof FIG. 5 takes the place of the circuit bordered by broken lines inFIG. 1, at the base of the circuit junction H of the secondary windingof the transformer 15. This circuit of FIG. 5, includes an inputtransistor T, which is connected, through a capacitor C,, to thecollector of the input transistor 13 of the multivibrator 12. Suchinterconnection of the transistor T, is accomplished through a couplingresistor 35, not shown in FIG. 5. At the same time, the base of thetransistor T, is connected to the positive voltage supply line 23,through a resistor R,. The collector of transistor T, is connected toone tenninal of a resistor R whereas the other terminal of this resistoris connected also to the positive voltage supply line 23. Anotherresistor R is connected between the same voltage supply line 23 and thebase of the transistor T A capacitor C is connected between thecollector of transistor T, and the base of transistor T In the quiescentstate of the circuit, the transistor T is maintained in the conductingstate. The collector of the transistor T is connected to a voltagedivider formed by resistors R and R connected in series. This seriesconnected combination of resistors is further connected between thepositive voltage supply line 23 and the collector of the transistor TThe cathode of a diode D is also connected to this collector oftransistor T,,. The anode of the diode D is, on the other hand,connected to the junction of two resistors R and R which are connectedin series and between the positive and negative voltage supply lines 23and 30, respectively. One terminal of the resistor R furthermore, isconnected to the anode ofthe diode D It will be understood that each ofthe elements described above, or two or more together, may also find auseful application in other types of constructions differing from thetypes described above.

While the invention has been illustrated and described as embodied in anarrangement for applying fuel injection corrections as a function ofspeed, in internal combustion engines, it is not intended to be limitedto the details shown, since various modifications and structural changesmay be made without departing in any way from the spirit of the presentinvention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.

1. A fuel injection control arrangement for an internal combustionengine comprising, in combination, electromagnetically controlled fuelinjection valve means; monostable multivibrator means connected to saidvalve means and applying pulse signals to said valve means, the durationof said pulse signals determining opening time interval of said valvemeans; control voltage-generating means connected to said monostablemultivibrator means for generating a control voltage to vary saidduration of said pulse signals as a function of the speed of saidengine, said control voltage having a characteristics variableperiodically in synchronism with said pulse signals; storage capacitormeans in said control voltagegenerating means for integrating saidcontrol voltage as a a function of time; at least two charging sourcesconnected to said capacitor means and having different internalresistances; and switching means connected to said charging sources forconnecting said sources in predetermined sequence to said capacitormeans.

2. The arrangement as defined in claim I, wherein said monostablemultivibrator means has an input transistor and an output transistor.

3. The arrangement as defined in claim 1, wherein said pulse signals arerectangular-shaped pulses.

4. The arrangement as defined in claim 1, wherein said switching meansdisconnects in sequence from said capacitor means the source previouslyconnected to said capacitor means upon connecting to said capacitormeans the subsequent one of said sources.

5. The arrangement as defined in claim 1 including a diode connectedbetween each source of said storage capacitor means.

6. The arrangement as defined in claim 5 including discharge meansconnected to said storage capacitor means and comprising a dischargediode; and a transistor with emitter-collector path connected in serieswith said discharge diode.

7. The arrangement as defined in claim 6 including voltage limitingmeans connected to said storage capacitor means for limiting the voltageacross said capacitor means, said voltagelimiting means comprising aclipping diode; voltage-dividing means connected to said clipping diodeand cooperating with said diode for limiting the charging voltage ofsaid capacitor means.

8. The arrangement as defined in claim 7 including a first auxiliarydiode connected between said capacitor means and said clipping diode;resistor means connected to the junction of said clipping diode and saidfirst auxiliary diode for limiting the charging current to saidcapacitor means; second voltagedividing means connected to said resistormeans and applying to said resistor means a voltage greater than thevoltage applied by said first-mentioned voltage dividing means to saidclipping diode.

9. The arrangement as defined in claim 5 including a first auxiliaryresistor and a second auxiliary resistor connected in series, saidseries connected auxiliary resistors being connected to the collector ofsaid transistor, the junction of said first and second auxiliaryresistors being connected to said discharge diode so that the dischargerate of said capacitor means is determined by said second auxiliaryresistor.

10. The arrangement as defined in claim 1, wherein at least of saidcharging sources comprises a transistor; a diode connected to saidtransistor and said charging capacitor means; and coupling capacitormeans connected to said transistor.

11. The arrangement as defined in claim 10, wherein said diode isconnected between said coupling capacitor means and the collector ofsaid transistor.

12. The arrangement as defined in claim 10, including a first resistorand a second resistor connected in series and to the collector of saidtransistor; and a third resistor connected in series with said diode andto the junction of said first and second resistors.

13. The arrangement as defined in claim 12 including voltage-dividingmeans; and a first auxiliary diode connected between the junction ofsaid third resistor and said diode and said voltage-dividing means.

14. The arrangement as defined in claim 13 including an auxiliarytransistor; and a coupling capacitor connected between the base of saidauxiliary transistor and the collector of said transistor.

15. The arrangement as defined in claim 14 including a second auxiliarydiode connected between said auxiliary transistor and said storagecapacitor means; and a third auxillary diode wlth anode connected to theanode of said second auxiliary diode, the cathode of said thirdauxiliary diode being connected to the collector of said transistor.

16 The arrangement as defined in claim 1 including a transistoremitter-follower with base connected to said storage capacitor means,the emitter of said emitter follower being connected to said monostablemultivibrator at a circuit junction where the potential influences theend of the unstable state of said multivibrator and the ends of saidpulse signals.

17. The arrangement as defined in claim 16 including a source ofoperating voltage; and a first resistor connected between the emitter ofsaid emitter-follower and said source of operating voltage.

18. The arrangement as defined in claim 16 including a resistorconnected between the emitter of said emitter-follower and said circuitjunction in said multivibrator.

19. The arrangement as defined in claim I, wherein said storagecapacitor means comprises two storage capacitors; and a diode connectedbetween said two storage capacitors for the coupling said storagecapacitors, the storage capacitor having the more positive voltage beingoperative and the other capacitor being inoperative.

20. The arrangement as defined in claim 19, including anemitter-follower transistor with base connected to said diode.

t i I! l

1. A fuel injection control arrangement for an internal combustionengine comprising, in combination, electromagnetically controlled fuelinjection valve means; monostable multivibrator means connected to saidvalve means and applying pulse signals to said valve means, the durationof said pulse signals determining opening time interval of said valvemeans; control voltagegenerating means connected to said monostablemultivibrator means for generating a control voltage to vary saidduration of said pulse signals as a function of the speed of saidengine, said control voltage having a characteristics variableperiodically in synchronism with said pulse signals; storage capacitormeans in said control voltage-generating means for integrating saidcontrol voltage as a a function of time; at least two charging sourcesconnected to said capacitor means and having different internalresistances; and switching means connected to said charging sources forconnecting said sources in predetermined sequence to said capacitormeans.
 2. The arrangement as defined in claim 1, wherein said monostablemultivibrator means has an input transistor and an output transistor. 3.The arrangement as defined in claim 1, wherein said pulse signals arerectangular-shaped pulses.
 4. The arrangement as defined in claim 1,wherein said switching means disconnects in sequence from said capacitormeans the source previously connected to said capacitor means uponconnecting to said capacitor means the subsequent one of said sources.5. The arrangement as defined in claim 1 including a diode connectedbetween each source and said storage capacitor means.
 6. The arrangementas defined in claim 5 including discharge means connected to saidstorage capacitor means and comprising a discharge diode; and atransistor with emitter-collector path connected in series with saiddischarge diode.
 7. The arrangement as defined in claim 6 includingvoltage limiting means connected to said storage capacitor means forlimiting the voltage across said capacitor means, said voltage-limitingmeans comprising a clipping diode; voltage-dividing means connected tosaid clipping diode and cooperating with said diode for limiting thecharging voltage of said capacitOr means.
 8. The arrangement as definedin claim 7 including a first auxiliary diode connected between saidcapacitor means and said clipping diode; resistor means connected to thejunction of said clipping diode and said first auxiliary diode forlimiting the charging current to said capacitor means; secondvoltage-dividing means connected to said resistor means and applying tosaid resistor means a voltage greater than the voltage applied by saidfirst-mentioned voltage dividing means to said clipping diode.
 9. Thearrangement as defined in claim 5 including a first auxiliary resistorand a second auxiliary resistor connected in series, said seriesconnected auxiliary resistors being connected to the collector of saidtransistor, the junction of said first and second auxiliary resistorsbeing connected to said discharge diode so that the discharge rate ofsaid capacitor means is determined by said second auxiliary resistor.10. The arrangement as defined in claim 1, wherein at least of saidcharging sources comprises a transistor; a diode connected to saidtransistor and said charging capacitor means; and coupling capacitormeans connected to said transistor.
 11. The arrangement as defined inclaim 10, wherein said diode is connected between said couplingcapacitor means and the collector of said transistor.
 12. Thearrangement as defined in claim 10, including a first resistor and asecond resistor connected in series and to the collector of saidtransistor; and a third resistor connected in series with said diode andto the junction of said first and second resistors.
 13. The arrangementas defined in claim 12 including voltage-dividing means; and a firstauxiliary diode connected between the junction of said third resistorand said diode and said voltage-dividing means.
 14. The arrangement asdefined in claim 13 including an auxiliary transistor; and a couplingcapacitor connected between the base of said auxiliary transistor andthe collector of said transistor.
 15. The arrangement as defined inclaim 14 including a second auxiliary diode connected between saidauxiliary transistor and said storage capacitor means; and a thirdauxiliary diode with anode connected to the anode of said secondauxiliary diode, the cathode of said third auxiliary diode beingconnected to the collector of said transistor. 16 The arrangement asdefined in claim 1 including a transistor emitter-follower with baseconnected to said storage capacitor means, the emitter of said emitterfollower being connected to said monostable multivibrator at a circuitjunction where the potential influences the end of the unstable state ofsaid multivibrator and the ends of said pulse signals.
 17. Thearrangement as defined in claim 16 including a source of operatingvoltage; and a first resistor connected between the emitter of saidemitter-follower and said source of operating voltage.
 18. Thearrangement as defined in claim 16 including a resistor connectedbetween the emitter of said emitter-follower and said circuit junctionin said multivibrator.
 19. The arrangement as defined in claim 1,wherein said storage capacitor means comprises two storage capacitors;and a diode connected between said two storage capacitors for thecoupling said storage capacitors, the storage capacitor having the morepositive voltage being operative and the other capacitor beinginoperative.
 20. The arrangement as defined in claim 19, including anemitter-follower transistor with base connected to said diode.